Despite the wealth of data supporting the hypothesis that central pre- synaptic serotonin (5-HT) function is reduced in male patients with suicidal and/or impulsive aggressive behaviors, little is conclusively known concerning the relationship between these behaviors and indices of post-synaptic or overall ("integrated" or "net") 5-HT function. Moreover, since little is known regarding the relationships among different putative indices of 5-HT function, our understanding of how to best interpret these data is limited. Finally, since few studies of central 5-HT activity and impulsive aggressive behavior in female subjects have been performed, little is known regarding these issues in women and the possibility of a gender difference in these relationships remains to be tested. In order to address these issues we propose to conduct three parallel studies which assess the relationship between central 5-HT function and suicidal and impulsive aggressive behavior in a psychiatric and in a normal control population. We propose to examine three indices of central 5-HT function in male and female patients with DSM-III-R personality disorder (PD) and in age and sex matched normal controls. These indices include: a) lumbar CSF concentrations of 5-HIAA as an index of "pre-synaptic" 5-HT activity; b) PRL responses to the direct post-synaptic 5-HT agonist m- chlorophenylpiperazine (m-CPP) as an index of "post-synaptic" receptor function; and c) PRL responses to the 5-HT releasing/uptake-inhibiting agent d-fenfluramine (d-FEN) as an index of integrated "pre-/post-synaptic" function). We have chosen to study personality disorder patients as the experimental group because suicidal and impulsive aggressive behaviors exist across a wide continuum in this group and because of previous data which indicate that PD patients consistently demonstrate inverse relationships between indices of central 5-HT function and both suicidal and impulsive aggressive behavior. Based upon previous work, we hypothesize that: a) the proposed indices of central 5-HT function will be intercorrelated; b) CSF 5-HIAA concentrations (5-HT "pre-synaptic") and PRL responses to both m-CPP (5-HT "post- synaptic") and d-FEN (5-HT "integrated pre-/post-synaptic") will be inversely related to suicidal and impulsive aggressive in behaviors in both male and female PD patients; and c) relationships between the PRL response to d-FEN, as an index of "integrated pre-/post-synaptic" index of 5-HT function, and those observed between the above behavioral variables will be stronger than those observed with either CSF 5-HIAA 95-HT "pre-synaptic") or the PRL response to m-CPP ("post-synaptic").